Field of the Invention
The present invention relates to an articulated robotic arm, and more particularly to a wrist structure for an articulated robotic arm.
Description of the Prior Art
Robotic arms have found wide application in various equipments due to their versatility and superior operability. For example, the robotic arm used in machining industry can pick up and move objects to a processing machine to enable the objects to be processed by the processing machine in an automatic manner. The robotic arm can also be applied in medical field and controlled by a doctor to perform operation on patients. For a further example, the robotic arm can be used in game play to grab objects.
Referring to FIG. 1, which shows a robotic arm assembly disclosed in U.S. Publication No. 20110154938A1, in order to control the rotation of the motor inside the wrist joint 13, a plurality of cables are inserted from the interior of the arm joint 11 into the interior of the wrist joint 13 and connected to the motor. In order to prevent the cables from tangling as the wrist joint rotates, a rotary member 14 with a central hole 141 is disposed between the wrist joint 13 and the rotary member 14, so that the wire connected to the motor of the wrist joint can insert through the central hole 141 into the wrist joint. However, the rotary member 14 is disposed in the arm joint 11, which is likely to increase the length of the arm joint 11. Besides, the structural strength of the rotary member 14 is low, which results in a low torque capability and a restricted rotation angle of the wrist joint 13.
To solve the above problem, a hollow reduction gear is used to drive the wrist joint, so that cables can be inserted through the central hole of the hollow reduction gear into the wrist joint. However, the number of cables that can insert through the central hole is limited by the size of the central hole of the hollow reduction gear. Therefore, the cables for controlling the end of the arm have to be disposed outside the arm, as a result, the cables are likely to get tangled when the arm rotates.
To solve the problem of wire tangling, Japan Publication No. JP2006321026 discloses an industrial robot, wherein each of the motors is additionally provided with a matrix converter so as to reduce the number of cables inside the arm. An external 3-phase AC power source is connected in parallel to the power supply of the motors, so that the number of power cables inside the arm is reduced from 12 to 3, making it easier for the cables to pass through the central hole of the hollow reduction gear, and reducing the difficulty of wiring. However, the converters have to control voltage and current, which requires relatively complicated technology, thus making the system complicated.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.